Marco Rubio-Jeb Bush alliance sours in GOP primary faceoff

They've been allies for more than a decade. But now, ties between Marco Rubio and Jeb Bush are fraying as the Republican presidential campaign picks up.

In public, mentor Bush -- a former Florida governor -- and protege Rubio -- a U.S. senator and former Florida House speaker -- have avoided criticizing each other since Rubio announced his candidacy.

But Bush allies have started quietly spreading negative information about Sen. Rubio's record.

Also, supporters of the two Miami politicians are drawing contrasts between Rubio, a 43-year-old son of Cuban immigrants, and 62-year-old Bush, a member of one of the nation's most powerful political dynasties.

Says one Bush adviser who's close to Rubio: "Sparks are going to fly."